Apparatus, methods and articles of manufacture for packaging an integrated circuit with internal matching

ABSTRACT

An integrated circuit package houses and connects to a die to form an integrated circuit with internal matching. The package comprises a lead frame comprising at least one transmission line, a die paddle, and at least one input lead and at least one output lead. Bond wires connect select locations along the at least one transmission line to ground through impedance matching circuit components located within the integrated circuit to provide an impedance matching network associated with at least one of the output leads. The package may also substantially encapsulate the lead frame, while exposing the die paddle and the input/output leads.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 10/142,250 filed May 9, 2002, the entire disclosureof which is incorporated by reference herein.

FIELD OF THE INVENTION

[0002] The present invention relates to the field of semiconductordevices, and in particular to an integrated circuit with internalimpedance matching.

BACKGROUND OF THE INVENTION

[0003] In cellular telephones, radio frequency (R.F) power amplifiers(PA) are built using a semiconductor device (e.g., silicon or GaAs) thathas a low output impedance (e.g., less two ohms). 1 0 This impedanceneeds to be transformed to a higher impedance value (e.g., fifty ohms)to connect to filters, switches, diplexers and antennas in the rest ofthe radio. This impedance transformation network is typically referredto as the “output match.”

[0004] In addition to transforming a two-ohm impedance to fifty ohms,the output match is typically tuned at the harmonic frequencies toincrease efficiency and battery life (e.g., talk time) of the cellulartelephone. These harmonic frequencies extend up to 6 GHz. At thesefrequencies, the distance between the capacitors and other passivecomponents used to construct the output match is critical, for example adistance of 0.001″ is significant. For example, a vendor may specifydistances of 0.062″ and 0.416″ in one one-thousandth of an inch ofprecision between the capacitors and other passive components of theoutput matching network.

[0005] The harmonic frequencies present a second problem. The capacitorshave parasitic values that become significant at the harmonicfrequencies. Since the parasitic values differ from one manufacturer toanother, changing vendors for the same value component will yielddifferent results.

[0006] In producing high volumes (e.g., 30,000,000 per year) thesedependencies on a single vendor and tolerances of 0.001″ are costly tomanage. Therefore, there is a need for an improved technique forproviding an impedance matching network.

SUMMARY OF THE INVENTION

[0007] Briefly, according to an embodiment of the present invention, anintegrated circuit includes a die that is electrically connected to andhoused within a package. The package includes a lead frame comprising atransmission line, at least one input signal lead, and at least oneoutput signal lead that is connected to the transmission line. The dieprovides an output signal onto the transmission line. At least oneselect location along the transmission line is connected to a firstelectrical node through an impedance matching circuit within theintegrated circuit.

[0008] According to another embodiment of the present invention, anintegrated circuit package includes a lead frame comprising at least onetransmission line, at least one input signal lead, and at least oneoutput signal lead. At least one select location along the transmissionline is connected to a first electrical node through an impedancematching circuit within the integrated circuit package, wherein theimpedance matching circuit is associated with the output signal lead.

[0009] The impedance matching circuit may be located within theintegrated circuit. For example, in one embodiment, the impedancematching circuit may be connected between the at least one selectlocation along the transmission line and a pin of the lead frame.

[0010] In one embodiment, at least one select location along thetransmission line is wire bonded to a capacitor. The capacitance valueof the capacitor and the dimensions of the transmission line areselected to provide the desired matching circuit (i.e., outputimpedance).

[0011] Incorporating the transmission line into the lead frame avoidshaving to place the matching network outside of the integrated circuit.For example, etching and/or half-etching the lead frame to provide thetransmission line, and placing components (e.g., capacitors, inductors,etc.) of the impedance transform matching circuit on the integratedcircuit and connecting these components between select locations on thetransmission line and first electrical node (e.g., ground) is relativelyinexpensive.

[0012] These and other objects, features and advantages of the presentinvention will become more apparent in light of the following detaileddescription of preferred embodiments thereof, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a functional block diagram of a prior artmatching circuit configuration for an RF output signal;

[0014]FIG. 2 is a cut-a-way top view of a first integrated circuit thatincludes a first die, and a second die within a first plastic package;

[0015]FIG. 3 is a functional block diagram illustration of the internalmatching network associated with the first die illustrated in FIG. 2;

[0016]FIG. 4 is a cut-a-way top view of a lead frame of a secondintegrated circuit that provides at least one output signal;

[0017]FIG. 5 illustrates a section taken along line A-A in FIG. 4;

[0018]FIG. 6 illustrates a bottom view of the second plastic package ofFIG. 4;

[0019]FIG. 7 illustrates a side view of the package of FIG. 6;

[0020]FIG. 8 is a cut-a-way top view of a lead frame of a thirdintegrated circuit that includes an internal matching circuit locatedwithin a die;

[0021]FIG. 9 is a top view of the lead frame of FIG. 8 shown in crosshatch;

[0022]FIG. 10 is a bottom view of the led frame of FIG. 8 with exposedsections of the lead frame shown in cross hatch;

[0023]FIG. 11 is a cut-a-way top view of a lead frame of a fourthintegrated circuit that includes an internal matching network locatedbetween the die paddle and a first select location on the transmissionline;

[0024]FIG. 12 is a cut-a-way top view of a lead frame of a fifthintegrated circuit that includes a first internal matching networkcomponent located between the die and a first select location on thetransmission line, and a second internal matching network componentlocated between the die paddle and a second select location on thetransmission line;

[0025]FIG. 13 is a functional block diagram illustration of the internalmatching network associated with the integrated circuit of FIG. 12; and

[0026]FIG. 14 is a cut-a-way top view of a lead frame of a sixthintegrated circuit that includes an internal matching network locatedbetween a first select location on the transmission line and a groundedpin.

DETAILED DESCRIPTION OF THE INVENTION

[0027]FIG. 1 illustrates a functional block diagram of an exemplaryprior art matching circuit configuration 100 that provides an outputsignal on a line 102. In one embodiment the output signal on the line102 is from an RF power amplifier (PA) within an integrated circuit 104.The integrated circuit 104 provides the output signal on the line 102 toan impedance transformation network 106 (also referred to herein as a“matching network”), which provides an impedance matched output signalon a line 108. For example, the impedance matched output signal on theline 108 may for example have an output impedance of fifty ohms, whereasthe impedance of the signal on the line 102 may for example be two ohms.The impedance matching network 106 includes a plurality of capacitors C₁110 and C₂ 112 that are precisely positioned to provide the requiredimpedance transformation and harmonic filtering. For example, thecapacitor C₁ 110 is precisely positioned (e.g., to a 0.001″ tolerance)from edge 114 of the integrated circuit 104, while the distance betweencapacitors C₁ 110 and C₂ 112 is also precisely controlled. As set forthabove, these positioning constraints lead to a problematic andrelatively costly matching network that is external to the integratedcircuit 104.

[0028]FIG. 2 is a cut-a-way top view of a first integrated circuit 200that includes a first die 202, and a second die 204 within a plasticpackage. The first die 202 provides an output signal via bond wires 206,208 to a first transmission line 210 located on a lead frame (e.g.,etched copper). The second die 204 provides an output signal via bondwires 212, 214 to a second transmission line 216 located on the leadframe The lead frame also includes a plurality of input/output (I/O)leads (e.g., 218-222). Bond wires interconnect bonding pads on the diesand the I/O leads. According to an aspect of the present invention, thelead frame also includes at least one transmission line (e.g., 0.1 mmthick in non-exposed areas, and 0.2 mm thick in exposed areas) thatcooperates with circuit components within the integrated circuit toprovide an integrated circuit with internal matching. Specifically, inthis embodiment matching circuit components such as capacitors and/orinductors (not shown) located on the first die 202 are connected to thefirst transmission line 210. For example, a first capacitor located onthe first die 202 is connected to a first selected location on thetransmission line 210 by bond wires 230, 231. Two bond wires are shownin this embodiment for current handling. However, a skilled person willrecognize of course that more or less bond wires may be used to connectthe matching circuit component on the die to the transmission line,depending upon the current handling required. In addition, a secondcapacitor (now shown) may be located on the die 202 and connected to asecond location (e.g., location 240) on the transmission line 210 bybond wires (not shown) to provide a matching circuit that isfunctionally similar to the circuit 106 illustrated in FIG. 1. However,in the embodiment of FIG. 2, the matching network is located within theintegrated circuit. That is, the integrated circuit of FIG. 2 includesinternal matching.

[0029] The second die 204 may also include an internal matching networkthat is established by connecting a matching circuit component(s) withinthe second die 204, to the transmission line 216 for example via bondwires 242, 244.

[0030]FIG. 3 is a functional block diagram illustration of the internalmatching network associated with the first die 202 illustrated in FIG.2. For example an output amplifier 246 located on the die 202 providesan output signal that is conducted by the transmission line 210 to anI/O lead 248. A first lead of a capacitor 252 located on the die 202 isconnected to a first select location 254 on the transmission line 210via the bond wires 230, 231. A second lead of the capacitor 252 isconnected to a first electrical potential, for example ground.Significantly, this provides an impedance matching circuit 258 that islocated within the integrated circuit 200.

[0031]FIG. 4 is a cut-a-way top view of a second integrated circuit 300that includes a die (not shown in FIG. 4), that is placed onto a diepaddle 302 of a lead frame 306 (e.g., etched copper) that includesplurality of I/O leads (e.g., 308-314). Interconnect bonding padslocated on the die are connected for example via bond wires to the I/Oleads. The lead frame 306 also includes a first transmission line 320shown in cross hatch. In this embodiment, the package also includes asecond transmission line 322 that is also not exposed on the exterior ofthe package. The first transmission line 320 is associated with a firstoutput signal from the package while the second transmission line isassociated with a second output signal from the package. Matchingcircuit components such as capacitors and/or inductors (not shown)located on the die and associated with the first output signal, areconnected between a first electrical potential (e.g., ground) and atleast one select location on the first transmission line 320.

[0032]FIG. 5 illustrates a section taken along line A-A in FIG. 4. A die402 is located on the paddle 302, and at least one bond wire 404connects lead 313 and a bond pad (not shown) on the die 402. FIG. 6illustrates a bottom view of the second integrated circuit. As shown,the lead frame includes the paddle 302 and the plurality of I/O leads,for example 308-314. Referring to FIGS. 5 and 6, the package alsoincludes a plurality of exposed wire bond support structures 510-517that represent select locations along the transmission lines at whichthe matching circuit components may be connected. For example, in oneembodiment, these support structures (e.g., etched copper) areconnection points for bond wires between the matching components on thedie, and the transmission lines within the lead frame of the package.For example, bonding wire 430 (FIG. 5) runs between a matching component(e.g., a capacitor) on the die 402 and the support structure 511 (i.e.,a select location on the transmission line 320).

[0033]FIG. 7 is a side view of the package of FIG. 5.

[0034]FIG. 8 is a cut-a-way top view of a third integrated circuit 800that includes a die 802, and a lead frame 804 of a third plasticpackage. FIG. 9 is a top view of the lead frame 804 of FIG. 8 shown incross hatch. The lead frame 804 includes a die paddle 806 and aplurality of I/O leads 808-823. The lead frame also includes atransmission line 826 that connects an output 828 on the die 802 toselected I/O leads 808-812. In this embodiment, the die output 828 isconnected to the transmission line 826 by a plurality of bond wires 831.The die 802 includes at least one component (e.g., a capacitor,inductor, etc.) of an impedance matching/transformation network. Thenetwork matching component within the die is connected to a first selectlocation 830 along the transmission line 826. As a result, a circuitconfiguration as shown in FIG. 3 is provided. Depending upon theimpedance matching and filtering requirements, the matching circuitcomponent within the die 802 may be connected to the transmission line826 at one of a plurality of select locations 832-836 along thetransmission line, rather than at the selected location 830. In theembodiment of FIG. 8, the integrated circuit 800 is 4 mm×4 mm (i.e., L850 is equal to 4 cm). As shown in FIG. 8, the path length of thetransmission line 826 will vary pending upon the select location (e.g.,830) along the transmission line that the matching circuit component isconnected to.

[0035]FIG. 10 is a bottom view of the lead frame of FIG. 8 shown incross Hatch. In this view, support structures associated with the selectlocations 8′) 0, 836 along the transmission line 826 (FIG. 9) areexposed on the underside of the integrated circuit 800.

[0036]FIG. 11 is a cut-a-way top view of a fourth integrated circuit1100 that includes a die 1102, and a lead frame 1104 of a fourth plasticpackage. This embodiment is substantially the same as the embodimentillustrated in FIGS. 8-10, with the principal exception that an internalmatching network component 1106 (e.g., a capacitor) is located betweendie paddle 1108 and a first select location 1110 on the transmissionline 826. That is, the internal matching circuit component is notlocated on the die. However, the internal matching circuit is stillresident within the integrated circuit to provide the internal matching.

[0037]FIG. 12 is a cut-a-way top view of a fifth integrated circuit 1200that includes a die 1202, and a lead frame 1204 of a fifth plasticpackage. This embodiment is substantially the same as the embodimentsillustrated in FIGS. 8-10, and FIG. 1, with the principal exception thata first internal matching network component 1206 (e.g., a capacitor) islocated between a die paddle 1208 and a first select location 1210 onthe transmission line 826, and second internal matching networkcomponent (not shown) is located within the die 1202 and connected to asecond select location 1212 on the transmission line.

[0038]FIG. 13 is a functional block diagram illustration of the internalmatching network associated with the integrated circuit of FIG. 12. Forexample, an output amplifier 1302 located on the die 1202 provides anoutput signal that is conducted by the transmission line 826 to the I/Olead 808. A first lead of a capacitor 1306 located on the die 1202 isconnected to the second select location 1212 on the transmission line826 via bond wires 1314. A second lead of the capacitor 1306 on the dieis connected to a first electrical potential, for example ground. Afirst lead of the capacitor 1206 is connected to the first selectedlocation 1210 on the transmission line 826, while a second lead of thecapacitor 1206 is connected to the die paddle (i.e., ground).

[0039]FIG. 14 is a cut-a-way top view of a sixth integrated circuit 1400that includes a die 1402, and a lead frame 1404 of a sixth package. Thisembodiment is substantially the same as the embodiments illustrated inFIGS. 8-10, FIG. 11 and FIG. 12, with the principal exception that aninternal matching network component 1406 is located between a firstelectrical potential comprising a grounded pin 1408 and a selectlocation 1410 on the transmission line 1426. In FIG. 14, the internalmatching network component is illustrated as a capacitor, although itshould be understood that any other suitable components may be utilizedas well, such as, for example, an inductor. Similar to that describedabove in connection with the earlier embodiments, the package of thepresent embodiment may substantially encapsulate (or encase) theintegrated circuit where desired, such as, for instance, by anover-molding process utilizing any desired materials, for example,conventional thermoplastic or thermosetting materials, such as plastic,e.g., a plastic mold compound. For example, as with the otherembodiments of the present invention, certain portions of the integratedcircuit in the present embodiment may be substantially encapsulated,such as the lead frame, while certain other portions remain exposed,such as the die paddle and the input/output leads.

[0040] The internal matching network component 1406 illustrated in FIG.14 may also be connected in other embodiments to the transmission line1426 at locations other than location 1410 wherever that may be desired.Similarly, in other embodiments, the internal matching network component1406 may be connected to portions other than the grounded pin 1408. Inaddition, in other embodiments, multiple matching network components maybe utilized where desired, such as, for example, as illustrated in theembodiments shown in FIGS. 8-10 and FIG. 12.

[0041] Advantageously, embodiments of the present invention may providean integrated circuit and package for internal impedance matching, thusfor example freeing a handset manufacturer (or board manufacturer) fromhaving to provide room on the board for the impedance transformationmatching circuitry. In addition, embodiments of the present inventionmay provide a package defining a member substantially encapsulating theintegrated circuit, so as to provide a barrier that can inhibit thepenetration of moisture or other undesirable matter. In addition,embodiments of the present invention may utilize etched and/orhalf-etched features in the overall architecture of an integratedcircuit. For instance, as is illustrated in FIG. 5, components 313 and314 are examples of half etched features, which may be utilized wheredesired for interlocking of particular components.

[0042] Although the present invention has been discussed in the contextof a package for power amplifiers for wireless handsets, it iscontemplated that the many other applications will find it desirable toreplace applications that require impedance matching, conventionallyperformed on a circuit board or as lumped element components, withmatching circuitry contained within the integrated circuit.Advantageously, this obviates many of the manufacturability problemsassociated with having to precisely position the components of thematching circuit. In addition, although the matching network componentshave been connected between the transmission line and ground, the firstelectrical potential does not necessarily have to be ground.

[0043] Although the present invention has been shown and described withrespect to several preferred embodiments thereof, various changes,omissions and additions to the form and detail thereof, may be madetherein, without departing from the spirit and scope of the invention.

What is claimed is:
 1. An internally matched integrated circuit,comprising: a package that includes a lead frame comprising at least oneinput signal lead, at least one output signal lead, and at least onetransmission line that is connected to said at least one output signallead; and a die that is electrically connected to and housed within saidpackage, and provides a signal onto said at least one transmission line;wherein a select location along said at least one transmission line iselectrically connected to a first electrical potential through animpedance matching circuit located on said integrated circuit.
 2. Theinternally matched integrated circuit of claim 1, wherein said selectlocation along said transmission line and said impedance matchingcircuit are connected via at least one bond wire.
 3. The internallymatched integrated circuit of claim 2, wherein said impedance matchingcircuit comprises a capacitor.
 4. The internally matched integratedcircuit of claim 2, wherein said impedance matching circuit compromisesan inductor.
 5. The internally matched integrated circuit of claim 2,wherein said die comprises a GaAs device.
 6. The internally matchedintegrated circuit of claim 2, wherein said die comprises a silicon die.7. The internally matched integrated circuit of claim 1, wherein saidfirst electrical potential comprises a grounded pin.
 8. The internallymatched integrated circuit of claim 1, wherein said packagesubstantially encases said lead frame.
 9. The internally matchedintegrated circuit of claim 1, wherein said package is plastic.
 10. Theinternally matched integrated circuit of claim 1, wherein said dieprovides at least one of an input signal or an output signal onto saidat least one transmission line.
 11. An internally matched integratedcircuit, comprising: a package that includes a lead frame comprising atleast one transmission line, a die paddle, at least one input signallead, and at least one output signal lead that is connected to said atleast one transmission line; and a die that is electrically connected toand housed within said package, and provides a signal onto said at leastone transmission line; wherein at least one select location on said atleast one transmission line is electrically connected to a firstelectrical potential through an impedance matching circuit.
 12. Theinternally matched integrated circuit of claim 11, wherein saidimpedance matching circuit comprises a capacitor having a first leadconnected to said select location along said transmission line, and asecond lead connected to said first electrical potential.
 13. Theinternally matched integrated claim of claim 11, wherein said impedancematching circuit comprises an inductor having a first lead connected tosaid select location along said transmission line, and a second leadconnected to said first electrical potential.
 14. The internally matchedintegrated circuit of claim 11, wherein said impedance matching circuitincludes a first lead connected to said select location along saidtransmission line, and a second lead connected to said first electricalpotential.
 15. The internally matched integrated circuit of claim 11,wherein said transmission line has a length of at least one millimeter.16. The internally matched integrated circuit of claim 11, wherein saidfirst electrical potential comprises a grounded pin.
 17. The internallymatched integrated circuit of claim 11, wherein said packagesubstantially encases said lead frame.
 18. The internally matchedintegrated circuit of claim 11, wherein said package is plastic.
 19. Theinternally matched integrated circuit of claim 11, wherein said dieprovides at least one of an input signal or an output signal onto saidat least one transmission line.
 20. An integrated circuit package thathouses and electrically connects to a die to form an integrated circuitwith internal matching, said package comprising: a lead frame comprisinga transmission line, a die paddle, a plurality of input leads, and aplurality of output leads, at least one which is connected to saidtransmission line, wherein at least one select location along saidtransmission line is electrically connected to a first electrical nodethrough an impedance matching circuit contained within said package toprovide an impedance matching network associated with said at least oneof said output leads connected to said transmission line. a member thatsubstantially encases said lead frame, while exposing said die paddleand said input leads and said output leads.
 21. The integrated circuitpackage of claim 0.20, wherein said transmission line comprises at leastone of etched or half-etched copper.
 22. The integrated circuit packageof claim 20, wherein said impedance matching circuit comprises acapacitor.
 23. The integrated circuit package of claim 20, wherein saidimpedance matching circuit comprises an inductor.
 24. The integratedcircuit packager of claim 20, wherein said impedance matching circuit islocated on said integrated circuit.
 25. The integrated circuit packageof claim 20, wherein said first electrical node comprises a pin, andsaid impedance matching circuit includes a capacitor having a first leadconnected to said pin and a second lead connected to said location onsaid transmission line.
 26. An internally matched integrated circuitcomprising: a package that includes a lead frame comprising a pluralityof input leads and a plurality of output leads, and at least onetransmission line that is connected to at least one of said outputleads; and a die that is electrically connected to and housed withinsaid package, and provides a signal onto said at least one transmissionline; wherein a select location along said at least one transmissionline is electrically connected to a first electrical potential throughan impedance matching circuit located within the integrated circuit. 27.The internally matched integrated circuit of claim 26, wherein saidpackage substantially encases said lead frame.
 28. The internallymatched integrated circuit of claim 26, wherein said package is plastic.29. The internally matched integrated circuit of claim 26, wherein saiddie provides at least one of an input signal or an output signal ontosaid at least one transmission line.
 30. The internally matchedintegrated circuit of claim 26, wherein said die is GaAs.
 31. Theintegrated circuit package of claim 26, wherein said transmission linecomprises at least one of etched or half-etched copper.
 32. Theinternally matched integrated circuit of claim 26, wherein said firstelectrical potential comprises a grounded pin.